TWI672307B - Organic electric field light-emitting element - Google Patents

Abstract

The invention provides an organic EL element with low driving voltage, high luminous efficiency, and long life. In an organic electric field light-emitting device including a light-emitting layer between an opposing anode and a cathode, the light-emitting layer includes a host material and a light-emitting dopant material, and the host material is a material in which a first body and a second body are mixed. The host is selected from compounds in which a diphenyltriazinyl group is bonded to one nitrogen of the indolocarbazole ring, and one or more phenyl groups are substituted on the phenyl group of the diphenyltriazinyl group; the second host is selected An aromatic hydrocarbon group is bonded to two nitrogens of the biscarbazole ring, and at least one of the aromatic hydrocarbon groups is a compound having a condensed aromatic hydrocarbon group.

Description

Organic electric field light emitting element

The present invention relates to an organic electric field light emitting device (referred to as an "organic EL device").

By applying a voltage to the organic EL element, holes are injected into the light emitting layer from the anode, and electrons are injected into the light emitting layer from the cathode. Furthermore, in the light emitting layer, the injected holes and electrons recombine to generate excitons. At this time, singlet excitons and triplet excitons are generated at a ratio of 1: 3 according to the statistical rule of electron spin. It can be said that the limit of the internal quantum efficiency is 25% using a fluorescent light-emitting organic EL element that emits light using a singlet exciton. On the other hand, it has been found that when a phosphorescent light-emitting organic EL element using light emitted from a triplet exciton efficiently performs intersystem crossing from a singlet exciton, the internal quantum efficiency is improved to 100%.

However, regarding the phosphorescent light-emitting organic EL element, prolonging the life has become a technical issue.

Furthermore, a highly efficient organic EL element utilizing delayed fluorescence has recently been developed. For example, Patent Document 1 discloses an organic EL device that utilizes a triplet-triplet fusion (TTF) mechanism, which is one of the mechanisms that delay fluorescence. The TTF mechanism is based on the phenomenon that a singlet exciton is generated by the collision of two triplet excitons. It is believed that the internal quantum efficiency is theoretically increased to 40%. However, it is inefficient compared to a phosphorescent organic EL element, and therefore, More efficient improvements are required.

On the other hand, Patent Document 2 discloses an organic EL element using a Thermally Activated Delayed Fluorescence (TADF) mechanism. The TADF mechanism uses the following phenomenon: in a material with a small energy difference between the singlet energy level and the triplet energy level, an inverse intersystem crossing from a triplet exciton to a singlet exciton; The internal quantum efficiency is increased to 100%. However, similarly to the phosphorescent light-emitting element, further improvement in lifetime characteristics is required.

[Prior Art Literature]

[Patent Document 1] WO2010 / 134350 A1

[Patent Document 2] WO2011 / 070963 A1

[Patent Document 3] WO2008 / 056746 A1

[Patent Document 4] Japanese Patent Laid-Open No. 2003-133075

[Patent Document 5] WO2013 / 062075 A1

[Patent Document 6] US2014 / 0374728 A1

[Patent Document 7] US2014 / 0197386 A1

[Patent Document 8] US2015 / 0001488 A1

[Patent Document 9] WO2011 / 136755 A1

Patent Document 3 discloses an indolocarbazole compound as a host material. Patent Document 4 discloses use of a biscarbazole compound as a host material.

Patent Documents 5 and 6 disclose the use of biscarbazole compounds as Use with mixed subjects. Patent Documents 7 and 8 disclose the use of an indolocarbazole compound and a biscarbazole compound as a mixed host.

Patent Document 9 discloses the use of a host material in which a plurality of hosts including an indolocarbazole compound are mixed in advance.

However, none of the above is sufficient, and further improvements are expected.

In order to apply an organic EL element to a display element such as a flat panel display or a light source, it is necessary to sufficiently ensure the stability during driving while improving the light emitting efficiency of the element. The present invention has been made in view of the foregoing circumstances, and an object thereof is to provide a practically useful organic EL element having a low driving voltage, high efficiency, and high driving stability.

The present invention is an organic EL element, which is an organic EL element including one or more light emitting layers between opposing anodes and cathodes, characterized in that at least one light emitting layer contains a member selected from the group consisting of the following formula (1) The first host of the compound and the second host selected from the compound represented by the following general formula (2), and a light-emitting dopant.

[Chemical 1]

(Here, ring A is an aromatic hydrocarbon ring represented by formula (1a), ring B is a heterocyclic ring represented by formula (1b), and ring A and ring B are each condensed with an adjacent ring at an arbitrary position.

Ar ¹ is phenyl, biphenyl, or bitriphenyl.

R is independently an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic heterocyclic group having 3 to 12 carbon atoms.

a, b, and c represent substitution numbers, and each independently represents an integer of 0 to 3.

m and n represent the number of substitutions, each independently represents an integer of 0 to 2, and m + n represents an integer of 1 or more)

[Chemical 2]

(Here, Ar ² and Ar ³ represent an aromatic hydrocarbon group having 6 to 14 carbon atoms, or two to three aromatic hydrocarbon groups connected to each other, and at least one of Ar ² and Ar ³ represents a condensed aromatic hydrocarbon group. )

As a preferred embodiment of the general formula (2), there is a general formula (3).

Ar general formula (3) Ar ² and Ar ³ in the general formula (2) is ² and Ar ³ are synonymous. Furthermore, it is more preferable that Ar ² is any of a naphthyl group and a phenanthryl group.

It is preferable that the first body and the second body are pre-mixed before evaporation so that use. In addition, it is preferable that a difference between the 50% weight reduction temperature of the first body and the second body is within 20 ° C, or the ratio of the first body to the total weight of the first body and the second body is 20wt. % (Weight percentage) is more than 55 wt%.

The luminescent doping material may be a phosphorescent luminescent doping material, a fluorescent luminescent doping material, or a thermally activated delayed fluorescent luminescent doping material. Examples of the phosphorescent light-emitting doping material include an organometallic complex containing at least one metal selected from the group consisting of ruthenium, rhodium, palladium, silver, osmium, osmium, iridium, platinum, and gold.

The organic EL element is preferably provided with a hole blocking layer adjacent to the light emitting layer, and the hole blocking layer contains a compound represented by the general formula (1).

Since the organic EL element of the present invention contains a plurality of specific host materials in the light-emitting layer, it can be an organic EL element having a low driving voltage, high luminous efficiency, and long life.

1‧‧‧ substrate

2‧‧‧ anode

3‧‧‧ Hole injection layer

4‧‧‧ Hole Transmission Layer

5‧‧‧ luminescent layer

6‧‧‧ electron transmission layer

7‧‧‧ cathode

FIG. 1 is a schematic cross-sectional view showing an example of an organic EL element.

The organic EL element of the present invention has one or more light-emitting layers between the opposing anode and cathode, and at least one layer of the light-emitting layer includes a first host and a second host, and a light-emitting dopant. The first host is a compound represented by the general formula (1), and the second host is a compound represented by the general formula (2). This organic EL element includes an organic layer including a plurality of layers between opposing anodes and cathodes. At least one of the plurality of layers is a light emitting layer, and a plurality of light emitting layers may be present. Moreover, the light emitting layer may also include A vapor-deposited layer produced by vacuum vapor deposition.

The general formula (1) will be described.

Ring A is an aromatic hydrocarbon ring represented by formula (1a), ring B is a heterocyclic ring represented by formula (1b), and ring A and ring B are condensed with adjacent rings at arbitrary positions.

Ar ¹ represents phenyl, biphenyl, or bitriphenyl. Phenyl and biphenyl are preferred, and phenyl is more preferred. Here, biphenyl is a group represented by -Ph-Ph, and bitriphenyl is a group represented by -Ph-Ph-Ph or -Ph (-Ph) -Ph. Ph is phenyl or phenyl.

R independently represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic heterocyclic group having 3 to 12 carbon atoms. Preferred is an aliphatic hydrocarbon group having 1 to 8 carbon atoms, a phenyl group, or an aromatic heterocyclic group having 3 to 9 carbon atoms. More preferred are aliphatic hydrocarbon groups having 1 to 6 carbon atoms, phenyl groups, or aromatic heterocyclic groups having 3 to 6 carbon atoms.

Specific examples of the aliphatic hydrocarbon group having 1 to 10 carbon atoms include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl.

Specific examples of the aromatic hydrocarbon group having 6 to 10 carbon atoms or the aromatic heterocyclic group having 3 to 12 carbon atoms include benzene, naphthalene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, Pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, oxazole, oxadiazole, quinoline, isoquinoline, quinoxaline, quinazoline, oxadiazole Azole, thiadiazole, benzotriazine, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzene Benzoisothiazole, benzothiadiazole, dibenzofuran, dibenzothiophene, di An aromatic group formed by removing one H from benzoselenophene or carbazole. Preferred examples include benzene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, oxazole Azole, oxadiazole, quinoline, isoquinoline, quinoxaline, quinazoline, oxadiazole, thiadiazole, benzotriazine, phthalazine, tetrazole, indole, benzofuran, benzothiophene , Benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzoisothiazole, or benzothiadiazole. More preferred examples include benzene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, oxazole Azole or oxadiazole.

a, b, and c each represent a substitution number, and each independently represents an integer of 0 to 3, preferably an integer of 0 or 1. m and n each represent a substitution number, and each independently represents an integer of 0 to 2, preferably an integer of 0 or 1. m + n is an integer of 1 or more, and is preferably an integer of 1, 2, or 3.

Specific examples of the compound represented by the general formula (1) are shown below, but are not limited to these exemplary compounds.

[Chemical 4]

[Chemical 5]

[Chemical 6]

[Chemical 7]

[Chemical 8]

[Chemical 9]

[Chemical 10]

[Chemical 11]

[Chemical 12]

Next, the compound of the general formula (2) or the general formula (3) which becomes a 2nd main body is demonstrated. In the general formula (2) and the general formula (3), common symbols have the same meaning.

Ar ² and Ar ³ represent an aromatic hydrocarbon group having 6 to 14 carbon atoms, or a group in which two to three aromatic hydrocarbon groups are linked. An aromatic hydrocarbon group having 6 to 12 carbon atoms is preferred, and an aromatic hydrocarbon group having 6 to 10 carbon atoms is more preferred. At least one of Ar ² and Ar ³ is a condensed aromatic hydrocarbon group.

Specific examples of Ar ² and Ar ³ include a bonded aromatic group formed by removing one H from a compound in which benzene, naphthalene, anthracene, phenanthrene, fluorene, or two or three of these compounds are linked. Preferred examples include aromatic groups derived from benzene, naphthalene, anthracene, or phenanthrene, and more preferred are aromatic groups derived from benzene, naphthalene, or phenanthrene. Further preferably, Ar ² is naphthyl or phenanthryl. Here, the linked aromatic group is a group represented by a formula such as -Ar ⁵ -Ar ⁷ , -Ar ⁵ -Ar ⁶ -Ar ⁷ , or -Ar ⁵ (-Ar ⁶ ) -Ar ⁷ , Ar ⁵ , Ar ^6. Ar ^{7 is} independently an aromatic hydrocarbon group having 6 to 14 carbon atoms. Ar ⁵ is a divalent or trivalent radical, Ar ⁶ is a monovalent or divalent radical, and Ar ⁷ is a monovalent radical.

Specific examples of the compounds represented by the general formulae (2) to (3) are shown below. Examples are not limited to these exemplary compounds.

[Chemical 14]

[Chemical 15]

[Chemical 16]

[Chemical 17]

[Chemical 18]

[Chemical 19]

By using the first host selected from the compound represented by the general formula (1) and the second host selected from the compound represented by the general formula (2) as the host material of the light emitting layer, excellent Organic EL element. The method for forming the light-emitting layer is not limited, and is preferably formed by vapor deposition.

When formed by vapor deposition, the first body and the second body may be vapor-deposited and used from different vapor deposition sources, but it is preferable to perform pre-mixing to make a pre-mixture before vapor deposition. The light-emitting layer is formed by simultaneous vapor deposition of the premix from a vapor deposition source. In this case, it is also possible to mix the light-emitting dopant material required for forming the light-emitting layer or other hosts used as needed in the premix, but there may be a large difference in the temperature at which the vapor pressure is expected. Next, vapor deposition may be performed from other vapor deposition sources.

In addition, regarding the mixing ratio (weight ratio) of the first body and the second body, the ratio of the first body to the total of the first body and the second body may be 20% to 60%, and preferably 20 to 60%. %, Less than 55%, more preferably 40% to 50%.

Furthermore, it is preferable that the difference between the electron affinity (EA) of the first host and the second host is greater than 0.1 eV and less than 0.6 eV. The value of EA is The host material film was calculated using the following values: the value of the Ionization Potential (IP) obtained by photoelectron spectroscopy; and the value of the energy gap obtained by measuring the absorption spectrum and the absorption end.

Next, the structure of the organic EL element of the present invention will be described with reference to the drawings, but the structure of the organic EL element of the present invention is not limited to this.

1 is a cross-sectional view showing a configuration example of a general organic EL element used in the present invention, where 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 is a light emitting layer, 6 Indicates an electron transport layer, and 7 indicates a cathode. The organic EL element of the present invention may have an exciton blocking layer adjacent to the light emitting layer, and may also have an electron blocking layer between the light emitting layer and the hole injection layer. The exciton blocking layer can also be inserted on either the anode side or the cathode side of the light emitting layer, or it can be inserted on both sides at the same time. The organic EL element of the present invention includes an anode, a light-emitting layer, and a cathode as necessary layers, but may include a hole injection transport layer and an electron injection transport layer in addition to the necessary layers, and may further include a light-emitting layer and an electron. A hole blocking layer is provided between the injection transport layers. The hole injection transport layer refers to either or both of the hole injection layer and the hole transport layer, and the electron injection transport layer refers to either or both of the electron injection layer and the electron transport layer.

It can also have the structure opposite to FIG. 1, that is, the cathode 7, the electron transport layer 6, the light emitting layer 5, the hole transport layer 4, and the anode 2 are sequentially laminated on the substrate 1. Add, omit.

-Substrate-

The organic EL element of the present invention is preferably supported on a substrate. About the substrate There is no particular limitation, as long as it is convenient for users of organic EL elements, for example, a substrate including glass, transparent plastic, quartz, or the like can be used.

-anode-

As the anode material in the organic EL element, a material including a metal, an alloy, a conductive compound, or a mixture of these with a large work function (4 eV or more) can be preferably used. Specific examples of such an electrode material include metals such as Au, and conductive transparent materials such as CuI, Indium Tin Oxide (ITO), SnO ₂ , and ZnO. In addition, an amorphous material such as IDIXO (In ₂ O ₃ -ZnO) can also be used, and a material that can be made into a transparent conductive film. The anode can be formed into a thin film by such methods as vapor deposition or sputtering, and a desired shape pattern can be formed by a photolithography method, or when pattern accuracy is not required (about 100 μm or more). During the vapor deposition or sputtering of the electrode material, a pattern may be formed through a mask having a desired shape. Alternatively, when a coatable substance such as an organic conductive compound is used, a wet film formation method such as a printing method or a coating method may be used. In the case where light is taken out from the anode, it is desirable that the transmittance is greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. The film thickness also depends on the material, and is usually selected in the range of 10 nm to 1000 nm, preferably 10 nm to 200 nm.

-cathode-

On the other hand, as the cathode material, a material including a metal (also referred to as an “electron injection metal”), an alloy, a conductive compound, or a mixture thereof having a small work function (4 eV or less) can be used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, and aluminum / alumina (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals, etc. From the viewpoint of electron injection property and durability to oxidation, among these, a mixture of an electron injection metal and a second metal having a larger and more stable work function than the second metal, such as a magnesium / silver mixture, is suitable. , Magnesium / aluminum mixture, magnesium / indium mixture, aluminum / alumina (Al ₂ O ₃ ) mixture, lithium / aluminum mixture, aluminum, and the like. The cathode can be produced by forming the cathode material into a thin film by a method such as evaporation or sputtering. Moreover, as the cathode, the sheet resistance is preferably several hundreds Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, and preferably 50 nm to 200 nm. In addition, in order to transmit the emitted light, if either the anode or the cathode of the organic EL element is transparent or translucent, the luminous brightness is improved, which is advantageous.

In addition, after forming the metal in a thickness of 1 nm to 20 nm in the cathode, the conductive transparent materials listed in the description of the anode are formed thereon, whereby a transparent or translucent cathode can be produced, and by applying this This method can produce a transparent element having both an anode and a cathode.

-Light emitting layer-

The light-emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from each of the anode and the cathode. The light-emitting layer includes an organic light-emitting dopant and a host material.

As the host material in the light-emitting layer, a first host represented by the general formula (1) and a second host represented by the general formula (2) were used. Further, one known host material may be used or a plurality of types may be used in combination, and the amount of use may be 50% by weight or less, and preferably 35% by weight or less, based on the total of the host materials.

The first body and the second body can be vapor-deposited from different evaporation sources, or they can be pre-mixed to form a pre-mixture before evaporation, thereby simultaneously vaporizing the first body and the first body from one evaporation source. 2 the main body.

When the first body and the second body are pre-mixed and used, in order to produce an organic EL element having good characteristics with good reproducibility, it is desirable that the difference between the 50% weight reduction temperature (T ₅₀ ) is small. The 50% weight reduction temperature refers to a temperature increase from room temperature to 550 ° C at a rate of 10 ° C per minute in a thermogravimetric-differential thermal analysis (TG-DTA) measurement under a reduced pressure (50Pa) of a nitrogen stream. The temperature at which the weight is reduced by 50%. It is considered that vaporization or sublimation gasification occurs most strongly around this temperature.

It is preferable that the difference between the 50% weight reduction temperature of the first body and the second body is within 20 ° C, and more preferably within 15 ° C. As the pre-mixing method, a known method such as pulverization and mixing can be used, and it is desirable to mix as uniformly as possible.

When a phosphorescent dopant is used as the luminescent dopant, the phosphorescent dopant may be an organic metal complex containing an organic metal complex selected from the group consisting of ruthenium, rhodium, palladium, silver, At least one metal of rhenium, osmium, iridium, platinum, and gold. Specifically, the iridium complex described in "J. Am. Chem. Soc." 2001, 123, 4304 or Japanese Patent Publication No. 2013-53051 can be suitably used, but It is not limited to these.

The phosphorescent light-emitting doping material may contain only one kind in the light-emitting layer, or may contain two or more kinds. The content of the phosphorescent light-emitting doping material is preferably 0.1 wt% to 30 wt%, and more preferably 1 wt% to 20 wt% relative to the host material.

The phosphorescent light-emitting doping material is not particularly limited, and examples thereof include the following.

[Chemical 21]

When a fluorescent light emitting dopant is used as the light emitting dopant, the fluorescent light emitting dopant is not particularly limited, and examples thereof include a benzoxazole derivative, a benzothiazole derivative, and a benzimidazole derivative. , Styrylbenzene derivative, polyphenyl derivative, diphenylbutadiene derivative, tetraphenylbutadiene derivative, naphthalenedimethylimine derivative, coumarin derivative, condensation aromatic Compounds, purple ring ketone derivatives, oxadiazole derivatives, oxazine derivatives, aldehyde azine derivatives, pyrrolidine derivatives, cyclopentadiene derivatives, bisstyryl anthracene derivatives, quinacridone derivatives Compounds, pyrrolopyridine derivatives, thiadiazolopyridine derivatives, styrylamine derivatives, diketopyrrolopyrrole derivatives, aromatic dimethylidine compounds, 8-hydroxyquinolines Metal complexes of derivatives or metal complexes of pyrromethene derivatives, rare earth complexes, transition metal complexes and other metal complexes, such as polythiophene, polybenzene, polyphenylacetylene, etc. Polymer compounds, organic silane derivatives . Preferred examples include condensed aromatic derivatives, styryl derivatives, diketopyrrolopyrrole derivatives, oxazine derivatives, pyrromethene metal complexes, transition metal complexes, or lanthanides. Complexes, more preferably naphthalene, fluorene, , Biphenyl tribenzo, benzo [c] phenanthrene, benzo [a] anthracene, pentacene, pyrene, fluoranthene, fluoranthene, dibenzo [a, j] anthracene, dibenzo [a, h ] Anthracene, benzo [a] naphthalene, fused hexabenzene, naphtho [2,1-f] isoquinoline, α-naphthoridine, phenoxazole, quinolino [6,5-f] quine Phthaloline, benzonaphthothiophene, etc. These may have an alkyl group, an aryl group, an aromatic heterocyclic group, or a diarylamino group as a substituent.

The fluorescent light-emitting doping material may contain only one kind in the light-emitting layer, or may contain two or more kinds. The content of the fluorescent light-emitting doping material is preferably 0.1% to 20%, and more preferably 1% to 10%, relative to the host material.

When a thermally activated delayed fluorescent light-emitting dopant is used as the light-emitting dopant, the thermally activated delayed fluorescent light-emitting dopant is not particularly limited, and examples include metal complexes such as tin complexes and copper complexes. Or indolocarbazole derivatives described in WO2011 / 070963, cyanobenzene derivatives, carbazole derivatives described in Nature 2012, 492,234, natural photonics (Nature Photonics) The phenazine derivatives, oxadiazole derivatives, triazole derivatives, fluorene derivatives, phenoxazine derivatives, acridine derivatives and the like described in 2014, 8, 326.

The thermally activated delayed fluorescent light-emitting doping material is not particularly limited, and examples thereof include the following.

[Chemical 22]

The thermally activated delayed fluorescent light-emitting doping material may contain only one kind in the light-emitting layer, or may contain more than two kinds. Furthermore, the thermally activated delayed fluorescent light emitting dopant may be used in combination with a phosphorescent light emitting dopant or a fluorescent light emitting dopant. The content of the thermally activated delayed fluorescent light-emitting doping material is preferably 0.1% to 50%, and more preferably 1% to 30% relative to the host material.

-Injection layer-

The so-called "injection layer" is a layer provided between the electrode and the organic layer in order to reduce the driving voltage or increase the light emission brightness. There are a hole injection layer and an electron injection layer, and it can also exist in the anode and the light emitting layer or hole Between the transport layers, and between the cathode and the light-emitting layer or the electron transport layer. The injection layer can be set as required.

-Electric hole barrier layer-

The so-called "hole blocking layer", in a broad sense, has the function of an electron transport layer, and includes a hole blocking material that has a function of transmitting electrons and has a significantly lower ability to transmit holes. It can improve light emission by transmitting electrons and blocking holes. Recombination probability of electrons and holes in the layer.

The hole blocking layer preferably contains a compound represented by the general formula (1), and a known hole blocking layer material may be used.

-Electronic blocking layer-

The so-called "electron blocking layer", in a broad sense, has the function of a hole transport layer, which can increase the probability of recombination of electrons and holes in the light-emitting layer by transmitting holes and blocking electrons.

As a material of the electron blocking layer, a known electron blocking layer material can be used, and a material of a hole transporting layer described later can be used if necessary. The film thickness of the electron blocking layer is preferably 3 nm to 100 nm, and more preferably 5 nm to 30 nm.

-Exciton blocking layer-

The so-called "exciton blocking layer" is a layer used to block the exciton generated by the recombination of holes and electrons in the light-emitting layer from diffusing into the charge transport layer. By inserting this layer, the exciton can be efficiently converted. Closed in the light-emitting layer, the light-emitting efficiency of the element can be improved high. The exciton blocking layer may be inserted between two adjacent light-emitting layers in an element adjacent to the two or more light-emitting layers.

As the material of the exciton blocking layer, a known exciton blocking layer material can be used. Examples include 1,3-dicarbazolylbenzene (mCP) or bis (2-methyl-8-hydroxyquinoline) -4-phenylaluminum (III) (BAlq).

-Hole transmission layer-

The so-called "hole transmission layer" includes a hole transmission material having a function of transmitting holes. The hole transmission layer may be provided in a single layer or multiple layers.

The hole-transporting material is a material having any of injection or transmission of holes and barrier properties of electrons, and may be any of organic and inorganic substances. In the hole transport layer, any one of the conventionally known compounds can be selected and used. Examples of the hole transport material include porphyrin derivatives, arylamine derivatives, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, and pyrazoline. Ketone derivatives, phenylenediamine derivatives, arylamine derivatives, chalcone derivatives substituted with amine groups, oxazole derivatives, styryl anthracene derivatives, fluorenone derivatives, fluorene derivatives, fluorene derivatives Compounds, silazane derivatives, aniline copolymers, and conductive polymer oligomers, especially thiophene oligomers. Porphyrin derivatives, arylamine derivatives, and styrylamines are preferably used. The derivative is more preferably an arylamine compound.

-Electronic transport layer-

The so-called "electron transport layer" includes materials having a function of transmitting electrons, and the electron transport layer may be provided in a single layer or a plurality of layers.

Electron-transporting material (also doubles as a hole blocking material), only It is sufficient to have a function of transmitting electrons injected from the cathode to the light emitting layer. The electron transporting layer can be selected from any of the conventionally known compounds and used, and examples thereof include polycyclic aromatic derivatives such as naphthalene, anthracene, and morpholine, tris (8-hydroxyquinoline) aluminum (III) derivatives, and phosphine oxide Derivatives, nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiorane oxide derivatives, carbodiimide, sulfenylmethane derivatives, anthraquinone dimethane and anthrone derivatives, Pyridine derivatives, quinoline derivatives, oxadiazole derivatives, benzimidazole derivatives, benzothiazole derivatives, indolocarbazole derivatives, and the like. Alternatively, a polymer material that introduces these materials into a polymer chain or uses these materials as a main chain of a polymer may be used.

[Example]

Hereinafter, the present invention will be described in more detail through examples, but the present invention is not limited to these examples, and may be implemented in various forms as long as the gist is not exceeded.

Compound 1-8 (0.20 g) and compound 2-10 (0.80 g) were weighed out and mixed while mashing in a mortar to prepare a premix H1.

In the same manner, premixture H2 to premixture H9 were prepared using the first and second bodies shown in Table 2.

The types and blending ratios of the first body and the second body are shown in Table 2. The compound number corresponds to the number attached to the exemplified compound.

The chemical formulas of the compound A and the compound B used as a subject for comparison are shown next.

[Chemical 23]

Table 1 shows compound 1-8, compound 1-24, compound 1-28, compound 1-46, compound 1-57, compound 2-10, compound 2-16, compound 2-19, and compound A and compound 50% weight reduction of B (T ₅₀ ) and electron affinity (EA).

Example 1

Each thin film was laminated on a glass substrate on which an anode including ITO having a film thickness of 110 nm was formed with a vacuum degree of 4.0 × 10 ^-5 Pa by a vacuum evaporation method. First, HAT-CN was formed on ITO to a thickness of 25 nm as a hole injection layer, and NPD was formed to a thickness of 30 nm as a hole transport layer. Next, HT-1 was formed to a thickness of 10 nm as an electron blocking layer. Next, pre-mixture H1 as a host and Ir (ppy) ₃ as a light-emitting dopant were co-evaporated from different vapor deposition sources to form a light-emitting layer with a thickness of 40 nm. At this time, co-evaporation was performed under vapor deposition conditions where the concentration of Ir (ppy) ₃ was 10% by weight. Next, ET-1 was formed to a thickness of 20 nm as an electron transport layer. Further, lithium fluoride (LiF) was formed on the electron transport layer to a thickness of 1 nm as an electron injection layer. Finally, aluminum (Al) was formed on the electron injection layer to a thickness of 70 nm as a cathode, thereby fabricating an organic EL element.

Example 2 to Example 9

In Example 1, an organic EL device was produced in the same manner as in Example 1 except that any one of the pre-mixture H2 to the pre-mixture H9 was used.

Example 10

In Example 3, after forming the light-emitting layer, Compound 1-8 was formed to a thickness of 10 nm as a hole blocking layer, and ET-1 was formed to a thickness of 10 nm as an electron transport layer. 3 was performed in the same manner to produce an organic EL element.

Example 11

Each thin film was laminated on a glass substrate on which an anode including ITO having a film thickness of 110 nm was formed with a vacuum degree of 4.0 × 10 ^-5 Pa by a vacuum evaporation method. First, HAT-CN was formed on ITO to a thickness of 25 nm as a hole injection layer, and NPD was formed to a thickness of 30 nm as a hole transport layer. Next, HT-1 was formed to a thickness of 10 nm as an electron blocking layer. Next, compounds 1-8 as the first host, compounds 2-10 as the second host, and Ir (ppy) ₃ as a light-emitting dopant were co-evaporated from different vapor deposition sources to form a light-emitting layer of 40 nm. thickness of. At this time, co-evaporation was performed under vapor deposition conditions where the concentration of Ir (ppy) ₃ was 10% by weight and the weight ratio of the first body to the second body was 40:60. Next, ET-1 was formed to a thickness of 20 nm as an electron transport layer. Further, LiF was formed on the electron transport layer to a thickness of 1 nm as an electron injection layer. Finally, Al was formed on the electron injection layer to a thickness of 70 nm as a cathode, thereby fabricating an organic EL element.

Example 12

An organic EL device was produced in the same manner as in Example 11 except that Compound 1-8 was used as the first host and Compound 2-19 was used as the second host.

Example 13

In Example 11, an organic EL device was produced in the same manner as in Example 11 except that Compounds 1-24 were used as the first host and Compounds 2-16 were used as the second host.

Example 14

An organic EL device was produced in the same manner as in Example 11 except that Compound 1-46 was used as the first host and Compound 2-19 was used as the second host.

Example 15

Each thin film was laminated on a glass substrate on which an anode including ITO having a film thickness of 110 nm was formed with a vacuum degree of 4.0 × 10 ^-5 Pa by a vacuum evaporation method. First, HAT-CN was formed on ITO to a thickness of 25 nm as a hole injection layer, and NPD was formed to a thickness of 45 nm as a hole transport layer. Next, HT-1 was formed to a thickness of 10 nm as an electron blocking layer. Next, pre-mixture H2 as a main body and Ir (piq) ₂ acac as a light-emitting dopant were co-evaporated from different vapor deposition sources to form a light-emitting layer with a thickness of 40 nm. At this time, co-evaporation was performed under vapor deposition conditions where the concentration of Ir (piq) ₂ acac was 6.0 wt%. Compound 1-8 was further formed to a thickness of 10 nm as a hole blocking layer. Next, ET-1 was formed to a thickness of 27.5 nm as an electron transport layer. Then, LiF was formed on the electron transport layer to a thickness of 1 nm as an electron injection layer. Finally, Al was formed on the electron injection layer to a thickness of 70 nm as a cathode, thereby fabricating an organic EL element.

Example 16, Example 17

In Example 15, an organic EL device was produced in the same manner as in Example 15 except that either of the premixture H3 and the premixture H4 was used as a main body.

Example 18

Each thin film was laminated on a glass substrate on which an anode including ITO having a film thickness of 110 nm was formed with a vacuum degree of 4.0 × 10 ^-5 Pa by a vacuum evaporation method. First, HAT-CN was formed on ITO to a thickness of 25 nm as a hole injection layer, and NPD was formed to a thickness of 45 nm as a hole transport layer. Next, HT-1 was formed to a thickness of 10 nm as an electron blocking layer. Then, compounds 1-57 as the first host, compounds 2-16 as the second host, and Ir (piq) ₂ acac as a light-emitting dopant were co-evaporated from different vapor deposition sources to form the light-emitting layer as 40nm thickness. At this time, co-evaporation was performed under vapor deposition conditions where the concentration of Ir (piq) ₂ acac was 6.0 wt% and the weight ratio of the first body to the second body was 30:70. Compound 1-8 was further formed to a thickness of 10 nm as a hole blocking layer. Next, ET-1 was formed to a thickness of 27.5 nm as an electron transport layer. Then, LiF was formed on the electron transport layer to a thickness of 1 nm as an electron injection layer. Finally, Al was formed on the electron injection layer to a thickness of 70 nm as a cathode, thereby fabricating an organic EL element.

Example 19

In Example 18, an organic EL device was produced under the same conditions as in Example 18, except that co-evaporation was performed under the deposition conditions where the weight ratio of the first body to the second body was 40:60.

Example 20

In Example 18, an organic EL element was produced under the same conditions as in Example 18, except that co-evaporation was performed under the deposition conditions where the weight ratio of the first body to the second body was 50:50.

Comparative Example 1

In Example 1, an organic EL device was produced in the same manner as in Example 1 except that Compounds 1 to 8 were used alone as the host. The thickness of the light-emitting layer and the concentration of the light-emitting dopant are the same as those in Example 1.

Comparative Example 2 to Comparative Example 7

In Example 1, an organic EL device was produced in the same manner as in Example 1 except that the compounds shown in Table 2 were used alone as the host.

Comparative Example 8

In Example 11, an organic EL device was produced in the same manner as in Example 11 except that Compound 1-8 was used as the first host and Compound A was used as the second host.

Comparative Example 9

In Example 11, an organic EL device was produced in the same manner as in Example 11 except that Compound B was used as the first host and Compound 2-10 was used as the second host.

Comparative Example 10 to Comparative Example 11

In Example 15, an organic EL device was produced in the same manner as in Example 15 except that Compound 1-8 or Compound 1-57 was used alone as the host.

The compounds used in the examples are shown next.

[Chemical 24]

The types of the premix of the first body and the second body, the types of the first body and the second body, and their ratios are shown in Tables 2 and 3.

Regarding the organic EL elements produced in Examples 1 to 14 and Comparative Examples 1 to 9, a DC voltage was applied to an external power source connected to the organic EL elements. As a result, light emission spectra with a maximum wavelength of 530 nm were all observed. Ir (ppy) ₃ emits light. In addition, the organic EL elements produced in Examples 15 to 20 and Comparative Examples 10 to 11 all observed an emission spectrum with a maximum wavelength of 620 nm, and it was found that light emission from Ir (pic) ₂ acac was obtained.

The brightness, driving voltage, luminous efficiency, and brightness half-life of the produced organic EL element are shown in Tables 4 and 5. In the table, brightness, driving voltage, and luminous efficiency are values when the driving current is 20 mA / cm ² and are initial characteristics. In Table 4, LT70 is the time it takes for the brightness to decay to 70% of the initial brightness when the initial brightness is 9000 cd / m ² ; In Table 5, LT95 is the time when the initial brightness is 3700 cd / m ² to decay to The time taken for 95% of the initial brightness, these are life characteristics.

From Tables 4 and 5, it can be seen that if the first main body represented by the general formula (1) and the second main body represented by the general formula (2) are used in combination, the life characteristics are more obvious than when they are used separately. increase. It was also found that even if the first and second bodies are mixed, when one of them is not a compound of the general formula (1) or the general formula (2), the driving voltage is high and good life characteristics cannot be obtained.

In addition, it can be seen that if a compound represented by the general formula (1) is used as a hole blocking material as in Example 10 or Examples 15 to 18, life characteristics will increase.

Compound 1-8 (0.40 g), compound 2-10 (0.30 g), and PH-1 (0.30 g) were weighed out and mixed in a mortar while being mashed to prepare a premix H10.

Compound 1-8 (0.40 g), compound 2-10 (0.30 g), and PH-2 (0.30 g) were weighed out and mixed while mashing in a mortar to prepare a premix H11.

The blending ratio in pre-mixture H10 and pre-mixture H11 is 40% for the first body (Compound 1-8), 30% for the second body (Compound 2-10), and the third body (PH-1 Or PH-2) is 30%.

Example 21

In Example 1, an organic EL device was produced in the same manner as in Example 1 except that the premix H10 was used as a main component.

Example 22

In Example 1, an organic EL device was produced in the same manner as in Example 1 except that the premix H11 was used as a main component.

Example 21 About the organic EL element prepared in Example 22, a DC voltage is applied thereto on the external power supply, the results were observed emission spectrum maximum wavelength of 530nm, it was found to obtain light emission from Ir (ppy) ₃ in.

Table 6 shows the brightness, driving voltage, luminous efficiency, and brightness half-life of the produced organic EL element. In the table, brightness, driving voltage, and luminous efficiency are values when the driving current is 20 mA / cm ² and are initial characteristics. In the table, LT70 is the time it takes for the brightness to decay to 70% of the initial brightness when the initial brightness is 9000 cd / m ² , and it is a lifetime characteristic.

Claims (10)

An organic electric field light-emitting element comprising at least one light-emitting layer between an opposing anode and cathode, characterized in that at least one light-emitting layer contains a member selected from the following general formula (1) A first host of the compound, a second host selected from the compound represented by the following general formula (2), and a light-emitting dopant material;

Here, ring A is an aromatic hydrocarbon ring represented by formula (1a), ring B is a heterocyclic ring represented by formula (1b), and ring A and ring B are condensed with adjacent rings at any positions; Ar ¹ is Phenyl, biphenyl, or triphenyl; R is independently an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic heterocyclic group having 3 to 12 carbon atoms; a , B, c independently represent integers of 0 ~ 3; m and n independently represent integers of 0 ~ 2, m + n represent integers of 1 or more;

Here, Ar ² and Ar ³ represent an aromatic hydrocarbon group having 6 to 14 carbon atoms, or a group formed by connecting two to three of the aromatic hydrocarbon groups, and at least one of Ar ² and Ar ³ represents a condensed aromatic hydrocarbon group . The organic electroluminescent element as described in item 1 of the patent application, wherein the compound represented by the general formula (2) is a compound represented by the following general formula (3);

Here, Ar Ar ² and Ar ³ in the general formula (2) is ² and Ar ³ are synonymous. The organic electroluminescence device as described in item 1 of the patent application, wherein Ar ² is naphthyl or phenanthryl. The organic electroluminescence device according to item 1 of the patent application scope has a light-emitting layer obtained by vapor-depositing a host material including a premix of the first host and the second host. The organic electroluminescent device as described in item 1 of the patent application range, wherein the difference between the 50% weight reduction temperature of the first body and the second body is within 20 ° C. The organic electroluminescence element according to item 1 of the patent application range, wherein the ratio of the first body to the total of the first body and the second body is more than 20% by weight and less than 55% by weight. The organic electric field light-emitting element according to any one of the first to sixth patent application ranges, wherein the light-emitting dopant material is selected from the group consisting of ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and Organometallic complex of at least one metal in the group consisting of gold. The organic electric field light-emitting element according to any one of claims 1 to 6, wherein the light-emitting doping material is a thermally activated delayed fluorescent light-emitting doping material. The organic electroluminescent device as described in item 1 of the patent application range, wherein the difference in electron affinity between the first host and the second host is more than 0.1 eV and less than 0.6 eV. The organic electric field light-emitting device according to item 1 of the patent application range, wherein a hole blocking layer is provided adjacent to the light emitting layer, and the hole blocking layer contains a compound represented by the general formula (1).